The invention discloses a simple and efficient topic extracting method. According to the method, the speed of extracting the topic can be increased. The method comprises the following steps: S1) in the word/file stage, treating the rows/lines of some small blocks of a topic matrix at each calculating node, successively scanning each row/line assigned to the calculating node, and performing an accepting step and a proposing step on each row/line; and S2) judging if the iteration times reach a preset constant, if yes, stopping iteration, if not, adding 1 to the iteration times and repeating the steps S1 and S2.